With the development of communication industry, conventional copper cables adapted in the telecommunication system have been gradually replaced by more efficient and light-weighted optic fiber cables. However, due to the fragility of the optic fiber, the optic fiber cable requires more severe protection. In general, an optic fiber cable comprises an outer tube inside which three or four inner tubes are received. Each of the inner tubes has an optic fiber extending therethrough. Currently, the outer tube of the optic fiber cable is made of polyvinyl chloride and the inner tube is made of polyethylene.
In a practical installation of the optic fiber cable, the outer tube is first embedded under ground. Thereafter the inner tubes, each of which is comprised of a plurality of separate segments, are put into the outer tube segment by segment and the segments of the inner tubes are then interconnected by means of a connector which is referred to as "inner tube connector" herein. Finally, the optic fiber is inserted through each of the inner tubes by means of compressed air. The compressed air brings the optic fiber from one end of the inner tube to the opposite end. To effectively make use of the compressed air in moving the optic fiber through the inner tube, the inner tube has to be air-tight, namely, the inner tube has to be hermetic through the whole length thereof, including the connection made by the connector. Thus air-tightness of the connection between two segments of the inner tube is of vital importance in using compressed air to move the optic fiber through the inner tube.
In addition, the air-tightness of the inner tube connector is also important in protecting the optic fiber from being damaged by invasion of humidity, insects or unwanted foreign objects. Thus, how to efficiently and effectively connect two segments of an optic fiber inner tube in the working sites is a topic that requires continuous research and development for the optic fiber industry.
Further, in order to provide the connection between the inner tube segments with a sufficient strength to resist un-wanted separation of the inner tube segments from each other, the inner tube segments have to be securely and firmly attached to the connector once they are connected by the connector in order to resist the stretching force applied thereto.
In addition, since the inner tubes may be supplied by different manufacturers and since the tolerance of the outside diameter of the inner tubes usually has no strict requirement, the connector that is used to connect two inner tube segments has to accommodate the outside diameter tolerances of the inner tubes from different suppliers. For example, the inner tubes of a nominal outside diameter of one and a quarter inches that are currently available in the market usually have several different values of the actual outside diameter and the maximum difference therebetween may as large as 6 mm. The conventional inner tube connectors that are currently available are incapable to effectively handle the variations in the tolerance of the outside diameter of the inner tubes in providing an effective air-tightness between the inner tube segments.
Further, in order to allow the inner tube segments to be readily inserted into and secured to the connector, a radial clearance is usually provided between the connector casing and the inner tube segments which may cause improper axial alignment between the two inner tube segments that are connected by the connector. Thus the segment may be offset with respect to each other in the radial direction. This causes problems in inserting the optic fiber through segments of the inner tube.
To overcome the above problems, in U.S. patent application Ser. No. 08/825,234, now U.S. Pat. No. 5,832,158, filed on Mar. 29, 1997, the applicant proposed an inner tube connector which is effective in solving the above problems. However, the structure of such a connector still has drawbacks in providing a ready and trouble-free installation of the connector.
Thus, it is desirable to provide an improvement over the conventional optic fiber inner tube connector which allows the connector to be installed in a more ready and less trouble way.